Re: JsInterop and Java collections?

As Thomas says, it will be impossible to support passing any of the collection interfaces directly through to JS code. You might think however, that you could change the implementation of ArrayList to actually be a JS Array. I don't think this is possible either because an instance of ArrayList needs to fulfill the Java contract of being able to know which interfaces it implements. This is done by having special meta data attached to the object prototype. The minute you start touching the Array prototype you have the potential of incompatibility with existing JS code.

Having said that, it is totally possible to implement an adapter to make a JS array look like a List. Below is a very hacky way to do it (the example uses the Array JsNative interface I defined but you could do the same with JsArray)

native <E> List<E> asList(Array<E> a) /*-{      l = @java.util.ArrayList::new()()      l.@java.util.ArrayList::array = a;      return l;  }-*/;

    Array<String> jsArray = Array.create();
      jsArray.push("val1");      jsArray.push("val2");
      List lArray = asList(jsArray);

    //Any changes to lArray will reflect in jsArray and vice versa

      lArray.add("val3");      jsArray.push("val4");

I strongly do not recommend using  the above approach. A better way would be to create an adapter class that takes the native Array to wrap in the constructor and implements the List methods. I have implemented this in my library.

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